DE 196 46 318 A1 discloses a process for producing a fastener element having a plurality of interlocking means in the form of stalks having enlargements integral with a backing strip, these enlargements forming the interlocking heads. In the disclosed process preferably a thermoplastic in a plastic or liquid state is introduced into a gap between a press roller and a shaping roller, such shaping roller being provided with cavities open outward and inward and both rollers being rotated in opposite directions, so that the backing strip is formed in the gap between the rollers. The interlocking means, on the other hand, are produced in the cavities of the screen shaping roller. The shape of the interlocking heads may then be additionally modified by a subsequent calendering process. The interlocking heads produced in this manner may be in the form of circular, cylindrical, or oblate heads or in the form of an oblate polyhedron such as a hexagon. If the interlocking heads consist of a conventional plastic material such as a polyester or the like, they are especially sensitive to the amount of heat applied and may also be damaged by scratching or the like to the extent that they are no longer capable of performing their function.
The interlocking heads produced in this manner are used for interlocking with the customary interlocking loops of a corresponding fastener element. The detachable mechanical fastener is effected by interlocking for the purpose of the interlocking members and the interlocking loops of the two associated fastener elements as a whole. The interlocking takes place when the loops of the corresponding fastener element are engaged below the projections which are formed between the bottom of the interlocking heads and the associated stalks. The stalks are an integral component of the backing or backing strip and support the interlocking heads at their free ends. The interlocking heads are configured on their free ends or over their surface as small oblate bodies. During the interlocking process the loops are pressed down and accordingly flattened by the interlocking heads, with the result that they are not available at the outset for a successful interlocking process. A comparable situation also arises when the otherwise elevated loop material has already been flattened on the associated backing strip, so that to this extent the interlocking heads of the other fastener element encounter difficulty in engaging the loop. In situations such as this the disengagement strength values typical of fasteners are greatly reduced and fastening becomes correspondingly more difficult.
In order to deal with this disadvantage effectively, it has been proposed in the state of the art that the shaping or configuration of the interlocking heads be favorably affected in such a way that these disadvantages are at least in part offset. For example, WO 98/57565 presents a known production process for comparable fasteners, one in which the stalks integrated with the backing are delivered to a tapered shaping gap, a shaping roller with closed cylindrical circumference pressing the ends of the stalks flat to form interlocking heads. The round, oblate interlocking heads as thus produced are provided on their free ends, that is, over their upper sides, with incisions and notches. This has the result that the material of a head is weakened in the area in which the incisions or notches are made, to the extent that a tip is formed and the reduced tip points in the material become movable to form a hinge, to the extent that they slip past the loops directed toward them and can effect interlocking when they snap back to their initial position. In this way the disengagement strength values and accordingly fastening of the corresponding fastener elements is appreciably improved, but the process, to be carried out in multiple steps, is complex and accordingly cost-intensive. If the process as disclosed is applied to very small fastening means, also designated as “microfasteners” in technical language, this disclosed process can not be employed, since, when the notches or incisions are introduced into the material of the head, they then cut through this material, which consequently becomes unserviceable. In addition, the material of the head is sensitive to the action of heat and to scratching.
In contrast, another generic process proposed in EP 0 894 448 A1 is a process in which the respective interlocking head is provided on its free end with an additional head element of an adhesive containing an acrylate, in order to improve the fastening effect and the disengagement strength values. Known head elements consist essentially of a so-called “hot-melt” pressure-sensitive adhesive based on an acrylate. The adhesive in question for the head elements should ensure that better interlocking of the components will take place in addition to interlocking of the head elements with the loop material. It has been found, however, that, because of the adhesive property of the head elements, the loops are simply joined adhesively to the fastener element with the interlocking means and engagement with interlocking means in the form of interlocking heads is simply not even significant, so that the engagement is determined more or less by the adhesive itself and not by the respective interlocking means selected. Consequently, it is still desired to use engagement of the fastener element with the interlocking means because of the hot-melt adhesive, in the case of loop material fouled with baby powder, baby oil, or the like. However, an adhesive connection is effected in this manner rather than engagement by way of the interlocking means in the form of the interlocking heads themselves. Since the joining accordingly results essentially from the adhesive, the engagement or disengagement strength values thereby obtained are not to be considered adequate. In addition, the adhesive head element cannot protect the interlocking head itself from heat.